serialize: Broaden ignores of json tests

It was thought that these failures only happened on windows, turns out they
happen on any 32-bit machine.

cc #14064

src/libserialize/json.rs

@@ -3098,7 +3098,7 @@ fn last_event(src: &str) -> JsonEvent {
         }
     }
     #[test]
-    #[ignore(cfg(windows))] // FIXME(#14064)
+    #[ignore(cfg(target_word_size = "32"))] // FIXME(#14064)
     fn test_read_object_streaming() {
         assert_eq!(last_event("{ "),      Error(SyntaxError(EOFWhileParsingObject, 1, 3)));
         assert_eq!(last_event("{1"),      Error(SyntaxError(KeyMustBeAString,      1, 2)));
@@ -3170,7 +3170,7 @@ fn test_read_object_streaming() {
         );
     }
     #[test]
-    #[ignore(cfg(windows))] // FIXME(#14064)
+    #[ignore(cfg(target_word_size = "32"))] // FIXME(#14064)
     fn test_read_list_streaming() {
         assert_stream_equal(
             "[]",